Subnetted traffic issue

Reply
hfhighschool
L1 Bithead

Subnetted traffic issue

I am running my PA-2050 on layer 2. The system runs great except for one issue. My wireless zones are subnetted. The PA can see the subnetted traffic, allows it to go out, but the packets get lost on the return back. I know there is nothing wrong with any devices in the upstream since all other content filtering systems we have ran before never had a problem with the subnets. Any suggestions?


Accepted Solutions
reaper
L7 Applicator

Hi Steve

Looks like you have a lot of non-syn drops.. these are usually caused by asymmetric routing.

This could also explain why ping seems to work but tcp not so much, as ping is stateless and will usually find it way back regardless of which route it takes.

Can you give this cli command a shot to see if this improves your connectivity: > set session tcp-reject-non-syn no

Next step would be to figure out where the asymmetry lives, by going over each hop from the AP out to the internet and doublechecking routing tables (make sure there are both inbound and outbound routes for the wifi subnets and default gateways etc. on every single hop) and verifying if there's any static/faulty arp entries that could be interfering with proper routing.

kind regards

Tom

Tom Piens - PANgurus.com
Like my answer? check out my book! amazon.com/dp/1789956374

View solution in original post


All Replies
Abs
L3 Networker

Is this a new install or has it worked before? Are other networks connected to the PA affected? Can you ping your wireless subnets from the upstream device?

AK

hfhighschool
L1 Bithead

This is a new install. Our main production network is connected and works great. It's only the wireless subnets that are the issue. I can ping back from any upstream device back to the workstation without any issue. I can even tracert to any site such as google without any problems. I just can't get the return packets to get Internet access in these subnets.

Abs
L3 Networker

What's the upstream device?

sdurga
L6 Presenter

So if I understand correctly from your description the traffic is passing through the Paloalto in outbound direction and the return traffic hitting Paloalto and is getting blocked . Are you able to see the sessions on Paloalto ? If so how are the sessions, are they stuck in incomplete ? The weird thing is that you are saying the ping and the trace route from the upstream is working fine which makes me believe that you are having proper routes. Also please check your NAT and security policies.

Tx,
Sandeep T

hfhighschool
L1 Bithead

Cisco ASA 5520. Everything worked great with the current configs until we installed the PA. We had a Cymphonix content filter before this and didn't have any routing issues. The PA is using the same IP address as the previous filter so no routes would need to be updated. We had a Cisco tech verify the configs once more and they are very adamant that it's the PA that is the issue.

hfhighschool
L1 Bithead

Sandeep,

You are correct in your understanding. The session is visible and stuck in incomplete.

Steve

sdurga
L6 Presenter

If the session is incomplete means the TCP hand shake is not complete. So try to see the monitor logs on Paloalto and check if paloalto is dropping the return traffic. If you do not find anything useful there then you have to set your packet filters to match the traffic of our interest and run the counters to see if there is any drops and the reason for the same.

Once you have the filters correct try to run the following command from the cli to see the drop counters

"show counter global filter delta-yes packet filter yes | match drop"

Run this a couple of time with 10 seconds delay and look for the output. If you do find any drops you will the reason for the drops too.

I would advise you to open a ticket with support so we can help you !!!

hfhighschool
L1 Bithead

Here is the output that I get:

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_policy_nofwd                          2        0 drop      flow      session   Session setup: no destination zone from forwarding

flow_tcp_non_syn_drop                     88        1 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                       6637       76 drop      flow      forward   Packets dropped: no desitnation MAC

flow_fwd_l2_same_interface                 4        0 drop      flow      forward   Packets dropped: destination MAC on same interface

flow_action_close                         30        0 drop      flow      pktproc   TCP sessions closed via injecting RST

url_request_pkt_drop                       5        0 drop      url       pktproc   The number of packets get dropped because of waiting for url category request

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                     13        0 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                       1974       76 drop      flow      forward   Packets dropped: no desitnation MAC

flow_fwd_l2_same_interface                12        0 drop      flow      forward   Packets dropped: destination MAC on same interface

flow_action_close                          9        0 drop      flow      pktproc   TCP sessions closed via injecting RST

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      5        2 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        144       70 drop      flow      forward   Packets dropped: no desitnation MAC

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      1        0 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        165       62 drop      flow      forward   Packets dropped: no desitnation MAC

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      1        0 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        173       73 drop      flow      forward   Packets dropped: no desitnation MAC

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      9        2 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        270       86 drop      flow      forward   Packets dropped: no desitnation MAC

flow_action_close                          1        0 drop      flow      pktproc   TCP sessions closed via injecting RST

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                     10        2 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        329       80 drop      flow      forward   Packets dropped: no desitnation MAC

flow_action_close                          6        1 drop      flow      pktproc   TCP sessions closed via injecting RST

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_fwd_l2_nomac                        147       62 drop      flow      forward   Packets dropped: no desitnation MAC

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      1        0 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        311       96 drop      flow      forward   Packets dropped: no desitnation MAC

flow_action_close                          6        1 drop      flow      pktproc   TCP sessions closed via injecting RST

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      5        1 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        283       80 drop      flow      forward   Packets dropped: no desitnation MAC

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      3        1 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        226       76 drop      flow      forward   Packets dropped: no desitnation MAC

flow_fwd_l2_same_interface                 1        0 drop      flow      forward   Packets dropped: destination MAC on same interface

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      4        0 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        448       96 drop      flow      forward   Packets dropped: no desitnation MAC

url_request_pkt_drop                       1        0 drop      url       pktproc   The number of packets get dropped because of waiting for url category request

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      9        2 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        202       61 drop      flow      forward   Packets dropped: no desitnation MAC

flow_action_close                          1        0 drop      flow      pktproc   TCP sessions closed via injecting RST

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      6        1 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        261       74 drop      flow      forward   Packets dropped: no desitnation MAC

flow_fwd_l2_same_interface                 1        0 drop      flow      forward   Packets dropped: destination MAC on same interface

flow_action_close                          2        0 drop      flow      pktproc   TCP sessions closed via injecting RST

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      4        1 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        249       82 drop      flow      forward   Packets dropped: no desitnation MAC

admin@PA-2050> show counter global filter delta yes packet-filter yes | match drop

flow_tcp_non_syn_drop                      2        0 drop      flow      session   Packets dropped: non-SYN TCP without session match

flow_fwd_l2_nomac                        328       76 drop      flow      forward   Packets dropped: no desitnation MAC

reaper
L7 Applicator

Hi Steve

Looks like you have a lot of non-syn drops.. these are usually caused by asymmetric routing.

This could also explain why ping seems to work but tcp not so much, as ping is stateless and will usually find it way back regardless of which route it takes.

Can you give this cli command a shot to see if this improves your connectivity: > set session tcp-reject-non-syn no

Next step would be to figure out where the asymmetry lives, by going over each hop from the AP out to the internet and doublechecking routing tables (make sure there are both inbound and outbound routes for the wifi subnets and default gateways etc. on every single hop) and verifying if there's any static/faulty arp entries that could be interfering with proper routing.

kind regards

Tom

Tom Piens - PANgurus.com
Like my answer? check out my book! amazon.com/dp/1789956374

View solution in original post

Like what you see?

Show your appreciation!

Click Like if a post is helpful to you or if you just want to show your support.

Click Accept as Solution to acknowledge that the answer to your question has been provided.

The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!

These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the LIVEcommunity as a whole!

The LIVEcommunity thanks you for your participation!